1. Field of the Invention.
This invention relates to the manufacture of petroleum sulfonates especially useful to impart micellar characteristics to hydrocarbon and water mixtures. The sulfonatable feedstock is a gas oil having a particular molecular weight range, a particular A/AP ratio, etc. 3 is effected with liquid SO.sub.s diluted in EDC and the sulfonic acids are neutralized with preferably a monovalent cation-containing base.
2. Description of the Prior Art.
U.S. Pat. No. 3,254,714 to Gogarty et al teaches injection and displacement of a microemulsion made up with petroleum sulfonate, through an oil-bearing subterranean formation to recover crude oil therefrom. U.S. Pat. No. 3,497,006 to Jones et al teaches oil recovery processes using high water content, i.e. 55-.pi.% water, oil-external micellar dispersions composed of petroleum sulfonate having an average molecular weight range of about 350-520. Jones, in U.S. Pat. No. 3,506,071 uses water-external micellar dispersions to recover crude oil. U.S. Pat. No. 3,302,713 to Ahearn et al floods with an aqueous solution containing a petroleum sulfonate having an average molecular weight of 450-500. Ahearn's sulfonates are obtained by sulfonating with gaseous SO.sub.3 a hydrocarbon having a boiling point range of 700-1100.degree. F.
U.S. Pat. No. 3,373,808 to Patton waterfloods with sulfonates obtained by sulfonating a hydrocarbon (having a boiling point range of 500.degree.-1500.degree. F.) with gaseous SO.sub.3 or liquid SO.sub.3 trimmer. The sulfonate hydrocarbons occurring in this boiling point range have an average molecular weight of about 250-700. Patton teaches that polysulfonation can be obtained by increasing the reaction temperature and the molar ratio of the sulfonating agent. In Example II, his hydrocarbon feedstock is first blended with equal volumes of 1,2-dichloroethane and then sulfonated with an inert vapor containing 8% gaseous SO.sub.3 --an equal molar amount of SO.sub.3 is added per mole of sulfonatable hydrocarbon. The reaction mixture is then neutralized with an aqueous isopropanol solution containing sodium hydroxide, permitted to phase separate and the middle layer is recovered. The middle layer is evaporated of the dichloroethane and isopropanol to obtain the desired sulfonate product.
Patton in U.S. Pat. No. 3,373,808 teaches that only the molecular weight and API gravity of the feedstock need be specified. Applicants have found, however, that sulfonates from two different gas oils with nearly the same molecular weights and API gravities, e.g. Canadian and Michigan gas oils with molecular weights and API gravities at 60.degree. F. of 438-439 and 25-26, respectively, impart considerably different micellar characteristics to hydrocarbon and water mixtures. Therefore, the A/AP ratio of the gas oil feedstock which Applicants teach is critical.
U.S. Pat. No. 2,168,315 to Blummer extracts mahogany sulfonates from a sulfonate mixture containing entrained oil and inorganic salts by contacting the mixture with an aqueous isopropyl alcohol mixture while maintaining the pH of the mixture at 3-9; a first liquid layer free from inorganic salts and containing organic solvent and mahogany sulfonates plus entrained oil is obtained and a second layer containing water and inorganic salts is formed.
U.S. Pat. No. 2,828,331 to Marisic et al teaches sulfonating petroleum oils at 10.degree.-150.degree. F, by injecting SO.sub.3 into a hydrocarbon stream under turbulent flow. The SO.sub.3 stream and the hydrocarbon stream can be diluted with ehtylene chloride if desired.